A variety of configurations of projectile guns, such as BB guns and pellet guns, exist. Some configurations are spring-loaded and use the mechanical energy of a spring to eject the projectile at a high rate of speed. Other configurations rely on compressed gas as the power source for ejecting the projectile from a barrel of the gun. Projectile guns exist in rifle configurations and pistol or handgun configurations. Additionally, there are currently single-shot configurations, semi-automatic configurations, and fully automatic configurations in existence.
Most compressed-gas guns use the compressed gas inefficiently. Previous designs of compressed-gas projectile guns are often lossy, or use more compressed-gas used with each shot than needed. Gas use efficiency is important, particularly for guns that operate on CO2 cartridges, and for automatic and semi-automatic guns. Gas losses can reduce the operation time on a compressed gas power source, and can increase cost of use.